The present invention relates to a digital broadcast receiver, a recording apparatus and a data recording method which are suitably used in a digital satellite broadcast system for receiving signals of video data and audio data broadcasted in the form of an MPEG (Motion Picture Experts Group) 2 transport stream and recording/reproducing the MPEG2 transport stream thus received in a recording medium such as a digital video tape or the like.
Recently, the digital satellite broadcast system has just started to achieve widespread use. In the digital satellite broadcast system, digital video data and digital audio data contained in a digital satellite broadcast are compressed, and then transmitted in packets in the form of a transport stream based on the MPEG2 system (an MPEG2 transport stream). In order to receive such a digital satellite broadcast, a digital satellite broadcast receiving decoder referred to as an IRD (Integrated Receiver Decoder) is connected to a television receiver. The MPEG2 transport stream is received by a parabolic antenna and is demodulated by the IRD to extract video and audio packets of a desired program, and a video signal and an audio signal are decoded from the video and audio packets. The video signal and audio signal are then supplied from the IRD to the television receiver.
It has been proposed to equip an IEEE1394 digital interface to the IRD for receiving such a digital satellite broadcast. The IEEE1394 digital interface supports an isochronous transfer mode and an asynchronous transfer mode. In the isochronous transfer mode, a delay time of transmission is compensated, and it is suitably used to transmit a time-sequential data stream such as video data and audio data at a high speed. On the other hand, in the asynchronous transfer mode, it is guaranteed that data can be surely transmitted to a destination node, and thus it is suitably used to surely transmit data such as commands or the like.
When the IRD is equipped with the IEEE1394 digital interface, a digital satellite broadcast receiving and recording/reproducing system can be constructed by connecting the IRD and a recording/reproducing apparatus or the like to each other. If such a system is constructed, the MPEG2 transport stream transmitted with the digital satellite broadcast can be directly recorded/reproduced.
That is, under the recording operation, an MPEG2 transport stream received at the IRD side is transmitted to the recording/reproducing apparatus through the IEEE1394 digital interface, and it is directly recorded in a recording medium by the recording/reproducing apparatus. Under the reproducing operation, the MPEG2 transport stream is reproduced from the recording medium, and the MPEG2 transport stream thus reproduced is transmitted to the IRD through the IEEE1394 digital interface. The MPEG2 transport stream thus transmitted is decoded by the IRD.
When the IRD is equipped with the IEEE1394 digital interface and both the IRD and the recording/reproducing apparatus are connected to each other to construct the digital satellite broadcast receiving and recording/reproducing system as described above, it is expected that a digital video cassette recording/reproducing apparatus using a video cassette which is compatible with a conventional analog system is used as a recording/reproducing apparatus. With such a digital video cassette recording/reproducing apparatus, transport streams can be recorded at a recording rate of 14.1 Mpbs. In the case of an SDTV (Standard Definition TV) transport stream based on the NTSC system having an aspect ratio of 3:4 and 525 scanning lines, the transmission rate is, for example, equal to 8 Mbps, and thus if such a digital video cassette recording/reproducing apparatus is used, the SDTV transport stream can be directly recorded.
However, for a digital satellite broadcast system which will be developed in the future, it is planed that not only the SDTV broadcast, but also the HDTV (High Definition TV) broadcast will be carried out. The HDTV broadcast is defined as a broadcast based on a high definition television having an aspect ratio of 16:9 and 1125 scanning lines, and the transmission rate thereof is, for example, equal to 24 Mbps. Therefore, with the digital video cassette recording/reproducing apparatus having the recording rate of 14.1 Mbps as described above, MPEG2 streams transmitted in the HDTV system cannot be directly recorded.
Therefore, when an HDTV transport stream is recorded/reproduced by using such a digital video cassette recording/reproducing apparatus, the mode of the recording/reproducing apparatus is switched to a high-speed recording rate.
That is, the recording rate of such a digital video cassette recording/reproducing apparatus is equal to 14.1 Mbps as described above, and if the recording time is reduced to a half in the digital video cassette recording/reproducing apparatus as described above, double amount of data can be recorded. In this case, the recording rate is equal to 28.2 Mbps. The transmission rate of the HDTV stream is, for example, equal to 24 Mbps, and thus, if the recording rate is set to 28.2 Mbps, the HDTV stream can be sufficiently recorded.
The recording mode of 14.1 Mbps serving as the standard is called as an STD mode, and a recording mode which is achieved by reducing the recording time of the STD mode to a half to enhance the recording rate to 28.2 Mbps is called an HS mode.
If the HS mode whose recording rate is increased to be twice as high as that of the STD mode can be set in addition to the STD mode serving as the standard recording mode, both the SDTV stream having an aspect ratio of 4:3 and 525 scanning lines and the HDTV stream having an aspect ratio of 16:9 and 1125 scanning lines can be recorded. That is, when signals from the IRD are recorded by using the digital video cassette recording/reproducing apparatus in such a system, the STD mode is set if an SDTV broadcast is to be recorded, or the HS mode is set if an HDTV broadcast is to be recorded.
When the recording mode of the digital video cassette recording/reproducing apparatus is set in accordance with whether the broadcast to be recorded is SDTV or HDTV as described above, the recording mode is required to be accurately and correctly set before the digital video cassette recording/reproducing apparatus is allowed to perform the recording operation.
In the conventional system in which the IRD is connected to a digital video cassette recording/reproducing apparatus in which both the STD mode and the HS mode can be set, there may occur such a situation that the recording is started regardless of whether a correct recording mode is set or not.
That is, in such a system where the IRD is connected to a digital video cassette recording/reproducing apparatus through IEEE1394, the mode of the digital video cassette recording/reproducing apparatus can be set on the basis of a command from the IRD. When such a command is issued from the IRD, the digital video cassette recording/reproducing apparatus is set to a recordable state regardless of whether the recording mode corresponding to the transmission rate of a stream being transmitted is correctly set or not.
In this system, when a recording button of the digital video cassette recording/reproducing apparatus is pushed, the digital video cassette recording/reproducing apparatus is set to the recordable state regardless of whether the recording mode corresponding to the transmission rate of a stream being transmitted is correctly set or not.
As described above, in the conventional system a situation may occur such that the recording is started under the state that the right recording mode is not set. Accordingly, there may occur such a situation that the recording mode of the digital video cassette recording/reproducing apparatus may be set to the HS mode although an SDTV broadcast is to be recorded, so that the recording efficiency is wasted. Further, the recording mode of the digital video cassette recording/reproducing apparatus may be set to the STD mode although an HDTV broadcast is to be recorded, so that overflow of bits occurs and correct data cannot be recorded.